Diamond like carbon (DLC) films with different C–C sp2/sp3 ratios were prepared by tuning the N2 flow rate in a
filtered cathodic vacuum arc (FCVA) system. The increase of N2 flow rate facilitated the increase of C–C sp2/sp3
ratio (1.09–2.66), the growth of particle size (0.78–1.58 nm) and the improvement of surface roughness. The SBF
immersion results, as well as WCAs (77.57°~71.71°), hemolysis rate (0.14–1.00%) and cytotoxicity level (0)
demonstrated that the as-fabricated DLC film was promising for biomedical application. As a result of surface
charge effect, the apatite layers formed in the SBF increased with the increase of C–C sp2/sp3 ratio until 1.74 and
then showed a tiny decrease during 1.74–2.66. A raise of hemolysis and cytotoxicity was observed when sp2/sp3
ratio was increased. Moreover, a decrease of friction coefficient of Si surface induced by increasing sp2/sp3 ratio
was respectively evidenced in ambient air and SBF lubrication environments.